Molecularity of a Reaction

Write a very short note on bimolecular reaction.

$2 \mathrm{HI} \to {\mathrm{H}}_2+{\mathrm{I}}_2$ 

The above reaction is an example of 

$2 \mathrm{HI} \to {\mathrm{H}}_2+{\mathrm{I}}_2$ 

What is the molecularity of the above reaction?

Trimolecular reactions are uncommon because:

If two reactants take part in a reaction, then:

Give an example for trimolecular reaction ?

Define trimolecular or termolecular reaction.

Termolecular reactions involve simultaneous collision between _____ reacting species.(three/ four)

Which of the reactions shows this kind of example ?

$2\mathrm{NO} + {\mathrm{O}}_2 \to 2{\mathrm{NO}}_2$

Define unimolecuar reaction ?

Give an example for an unimolecular reaction.

If in a unimolecular reaction, $\text{A}\left(\mathrm{g}\right)⟶\text{Products}$ takes place according to the mechanism

I. $\text{A}+\text{A}\underset{{\text{k}}_{-1}}{\overset{{\text{k}}_1}{\rightleftharpoons }}{\text{A}}^{*}+\text{A}$

II. ${\text{A}}^{*}\underset{{\text{k}}_2}{⟶}\text{P}$

where ${\text{k}}_1\text{, }{\text{k}}_{-1}$ ${\text{k}}_2$ are the rate constants and P, $\mathrm{A}$ and ${\text{A}}^{*}$ stand for product molecule, normal molecules of reactants and activated molecules of reactants respectively.

Which of the following statements are correct?

For next two question please follow the same

 If in a unimolecular reaction, $\text{A}\left(\mathrm{g}\right)⟶$ products takes place according to the mechanism

I. $\text{A}+\text{A}\underset{{\text{k}}_{-1}}{\overset{{\text{k}}_1}{\rightleftharpoons }}{\text{A}}^{*}+\text{A}$

II. ${\text{A}}^{*}\underset{{\text{k}}_2}{⟶}\text{P}$

where ${\text{k}}_1\text{, }{\text{k}}_{-1}$ ${\text{k}}_2$ are the rate constants and P, $\mathrm{A}$ and ${\text{A}}^{*}$ stand for product molecule, normal molecules of reactants and activated molecules of reactants respectively.

Which of the following expressions are correct?

Consider the reaction ${\mathrm{Tl}}^{+}\left(\mathrm{aq}\right)+2{\mathrm{Ce}}^{4+}+\left(\mathrm{aq}\right)\to {\mathrm{Tl}}^{3+}+\left(\mathrm{aq}\right)+2{\mathrm{Ce}}^{3+}\left(\mathrm{aq}\right)$ 

The rate law for the reaction is rate =$\mathrm{k}$ $\left[{\mathrm{Ce}}^{4+}\right] \left[{\mathrm{Mn}}^{2+}\right].$

In the presence of ${\mathrm{Mn}}^{2+}$the reaction occurs in the following elementary steps:

${\mathrm{Ce}}^{4+ }\left(\mathrm{aq}\right)+{\mathrm{Mn}}^{2+}\left(\mathrm{aq}\right) \to {\mathrm{Ce}}^{3+}\left(\mathrm{aq}\right)+{\mathrm{Mn}}^{3+} \left(\mathrm{aq}\right)$

${\mathrm{Ce}}^{4+}\left(\mathrm{aq}\right)+{\mathrm{Mn}}^{3+}\left(\mathrm{aq}\right)\to {\mathrm{Ce}}^{3+}\left(\mathrm{aq}\right)+{\mathrm{Mn}}^{4+}\left(\mathrm{aq}\right)$

${\mathrm{Tl}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Mn}}^{4+}\left(\mathrm{aq}\right)⟶{\mathrm{Tl}}^{3+}\left(\mathrm{aq}\right)+{\mathrm{Mn}}^{2+}\left(\mathrm{aq}\right)$

Identify rate determining step.

The reaction between ${\mathrm{H}}_2 \left(\mathrm{g}\right)$ and $\mathrm{ICl} \left(\mathrm{g}\right)$occurs in the following steps:
$\text{ (i) }{\mathrm{H}}_2+\mathrm{ICl}⟶\mathrm{HI}+\mathrm{HCl}$

$\text{ (ii) }\mathrm{HI}+\mathrm{ICl}⟶{\mathrm{I}}_2+\mathrm{HCl}$

The reaction intermediate in the reaction is

The rate law for the reaction $2 {\mathrm{H}}_2 \left(\mathrm{g}\right) + 2\mathrm{NO} \left(\mathrm{g}\right) \to {\mathrm{N}}_2 \left(\mathrm{g}\right) + 2{\mathrm{H}}_2\mathrm{O} \left(\mathrm{g}\right)$ is given by rate $=\mathrm{K} \left[{\mathrm{H}}_2\right] [\mathrm{NO}{]}^2$. The reaction occurs in the following steps:

$$\begin{gathered} {\mathrm{H}}_2 + 2\mathrm{NO} \to {\mathrm{N}}_2\mathrm{O} + {\mathrm{H}}_2\mathrm{O} \\ {\mathrm{N}}_2\mathrm{O} + {\mathrm{H}}_2 \to {\mathrm{N}}_2 + {\mathrm{H}}_2\mathrm{O} \end{gathered}$$
Identify the slow step.

The rate law for the reaction $2 {\mathrm{H}}_2 \left(\mathrm{g}\right) + 2\mathrm{NO} \left(\mathrm{g}\right) \to {\mathrm{N}}_2 \left(\mathrm{g}\right) + 2{\mathrm{H}}_2\mathrm{O} \left(\mathrm{g}\right)$ is given by rate $=\mathrm{K} \left[{\mathrm{H}}_2\right] [\mathrm{NO}{]}^2$. The reaction occurs in the following steps:

${\mathrm{H}}_2 + 2\mathrm{NO} \to {\mathrm{N}}_2\mathrm{O} + {\mathrm{H}}_2\mathrm{O}$

$N_{2}O+H_2\to N_2+H_{2}O$

What is the role of ${\mathrm{N}}_2\mathrm{O}$ in the mechanism?

Molecularity of an elementary reaction

The rate law for the reaction $2\mathrm{NO}\left(\mathrm{g}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)\to 2\mathrm{NOCl}\left(\mathrm{g}\right)$ is given by rate $=\mathrm{k} \left[\mathrm{NO}\right] \left[{\mathrm{Cl}}_2\right]$ . The reaction occurs in the following steps:
(i) $\mathrm{NO}\left(\mathrm{g}\right)+{\mathrm{Cl}}_2\to {\mathrm{NOCl}}_2\left(\mathrm{g}\right)$.

(ii) ${\mathrm{NOCl}}_2\left(\mathrm{g}\right)+\mathrm{NO}\left(\mathrm{g}\right)\to 2\mathrm{NOCl}\left(\mathrm{g}\right)$.

Identify the rate determining step.

A certain reaction occurs in the following steps:

(i) $\mathrm{Cl}\left(\mathrm{g}\right)+{\mathrm{O}}_3\left(\mathrm{g}\right)\to \mathrm{ClO}\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

(ii) $\mathrm{ClO} \left(\mathrm{g}\right)+ \mathrm{O} \left(\mathrm{g}\right)\to \mathrm{Cl}\left(\mathrm{g}\right)+ {\mathrm{O}}_2 \left(\mathrm{g}\right)$
Identify the reaction intermediate.